1. Field of the Invention
The present invention relates to a stamping tool having a structured stamping surface, a casting mold, a method for producing a stamping tool or a casting mold having a structured stamping surface, and methods for structuring a surface of a work piece.
2. Description of Related Art
Stamping constitutes a non-cutting manufacturing method for producing a relief-like or structured surface on a work piece. A stamping tool with a profiled or structured stamping surface is used for this. The stamping surface is pressed with such a stamping force onto the surface to be structured of the work piece or rolled on it, so that the work piece becomes plastic and flows into depressions in the stamping tool or the stamping surface. Due to the considerable stamping forces employed, the stamping tool and the stamping surface are usually made of metal.
Further, molding is known. A casting mold with a structured molding face can be used for producing a cast work piece with a structured surface by casting.
In the present invention, nanometer range is understood to mean profiling or structuring with structural widths of less than 1000 nm, especially of less than 500 nm. The structural width designates the dimension by which individual structural elements, such as bumps, are repeated, that is, for example, the average distance of adjacent bumps from one another or of depressions from one another.
It is very expensive to manufacture a stamping tool with a very finely structured or profiled stamping surface. To create a so-called “moth eye structure”—evenly arranged, egg carton-like bumps—or fine grooves in the nanometer range, it is known from practice to use a lighting pattern with periodic intensity modulation for illuminating photosensitive material via two interfering laser beams. After the illuminated material develops, a periodic surface structure results, which is molded into other materials using various replication methods and finally into nickel, for example, by electroforming. This type of manufacturing is very expensive and is suited only for structuring even surfaces.
In the nanometer range, lithographic methods for structuring a stamping surface of a stamping tool can still only be used in a limited way. It should be noted here that the wavelength of the visible light alone is already 400 to 750 nm. In each case, lithographic methods are very costly.
German Patent DE 197 27 132 C2 discloses the manufacturing of a stamping tool by means of electrolytic machining. During electrolytic machining, a metallic stamping surface of the stamping tool is treated electrolytically, wherein, being an anode in a fast-flowing electrolyte, the metal of the stamping surface is located at a minimal distance opposite a cathode and is dissolved in surface terms. The metal or the stamping surface contains the structure determined by the form of the cathode, and the cathode thus forms a recipient vessel that is shaped electrochemically. German Patent DE 197 27 132 C2 also provides the use of a cylindrical rotation electrode, whose covering surface presents a negative form of the desired stamping structure. Here, too, there is considerable expense involved and structuring in the nanometre range is at least only partly possible.
The use of anodally oxidized surface layers made of aluminum or magnesium in casting molds to increase resistance is known from Swiss Patent CH 251 451. However, the forming of hollow chambers by oxidation for structuring a molded article in the nanometer range is not disclosed.
Forming hollow chambers by anodic oxidation of aluminum is described in published European Patent Application EP 0 931 859 A1, for example.
However, the related art does not provide a cost-effective solution to production of a work piece, like a stamped piece, or casting with a surface structured in the nanometer range.
Consequently, there is a need for a stamping tool, a casting mold, a method for manufacturing a stamping tool or a casting mold, a method for structuring a surface of a work piece and a method for using a surface layer provided with open hollow chambers, wherein structuring in the nanometer range is enabled in a simple and cost-effective manner.